1. Field of the Invention
The present invention relates to a method of manufacturing a substrate used for a liquid discharge head which applies energy to a liquid, such as ink, thereby discharging the liquid.
2. Description of the Related Art
Generally, an ink jet head is heated by a pressure generator, for example, a heater board for discharging ink, whereby components of an ink composition are evaporated to generate pressure to discharge ink. Additionally, generally, ink is supplied from the rear face of a substrate for an ink jet head in which the pressure generator is provided. For this reason, the ink jet head substrate is provided with an ink supply port for allowing a surface and a rear face to fluidly communicate with each other.
As a method for forming an ink supply port in a substrate for an ink jet head, for example, U.S. Pat. No. 5,658,471 discloses using anisotropic etching by taking advantage of the features of a single crystal silicon substrate that is a substrate material for an ink jet head. Additionally, US Patent Application Publication No. 2005/0103758 discloses a method of using laser beam machining.
In a case where a substrate for an ink jet head described in US Patent Application Publication No. 2005/0103758 is machined using a laser to form an ink supply port, an ink supply port which has a wall surface vertical to a substrate surface can be obtained. However, in a single crystal silicon substrate which is widely used as a material for the substrate for an ink jet head, the surface vertical to the substrate surface generally does not become a crystal plane. For this reason, depending on the composition of ink, the wall surface of the ink supply port may be etched by the ink. If components of the substrate are eluted into ink, the drawing performance of the ink jet head may be unstable, or defects such as clogging of an ink flow channel may occur.
On the other hand, according to the method of forming an ink supply port by anisotropic etching disclosed in U.S. Pat. No. 5,658,471, the wall surface of the ink supply port can be a crystal plane which is stable against ink, and the aforementioned problem does not occur. However, in the method of forming an ink supply port in a substrate for an ink jet head made from single crystal silicon as disclosed in Patent Document 1, an etching mask was given to one face (rear face) of the substrate, and anisotropic etching is performed from one side (rear face). Therefore, the cross-section of an ink supply port 60 which communicates with discharge ports 30 is formed in a tapered shape due to the inclination of the crystal plane to the substrate surface. Therefore, the opening width in the rear face becomes significantly larger than the opening width in the surface of the substrate for an ink jet head (refer to FIG. 2). As a result, there is a problem in that size of the substrate for an ink jet head cannot be made small.